255 results about "Noise power" patented technology

The invention discloses a cable partial discharge signal noise separation mode identification method and system, and particularly relates to the technical field of cable partial discharge detection, in a multi-cable stacking environment, partial discharge signals are synchronously collected through multiple types of sensors such as a high-frequency current sensor, an ultrasonic sensor and an electromagnetic antenna; performing band-pass filtering, wavelet denoising and multi-channel synchronous alignment on the acquired signals to suppress background noise and retain key features of partial discharge pulses; separating the mixed signals by adopting independent component analysis; calculating a decision coefficient based on an inter-channel correlation coefficient, a signal-noise power ratio and an amplitude dynamic range, and judging whether to introduce a denoising method based on deep learning; for the waveform after noise separation, executing an amplitude re-calibration process so as to correct amplitude scaling uncertainty, and extracting multi-dimensional time domain, frequency domain and phase features; and a support vector machine and other machine learning algorithms are combined to realize automatic identification of partial discharge types.

The invention discloses a multi-bandwidth spectrum data signal adaptive extraction method based on a signal-to-noise ratio threshold, and relates to the technical field of spectrum signal extraction. The frequency spectrum data collection covers 30MHz-6GHz, the sampling rate is 20MHz, 16-bit quantization is realized, and the hardware fluctuation is eliminated through the dual-channel design; according to noise floor estimation, 50 frames of no-signal samples are taken, mean value calculation is carried out through a sliding window, then median filtering is carried out, and the noise power and confidence interval of each frequency point are obtained; basic values are set for a signal-to-noise ratio threshold according to frequency bands, dynamic adjustment is performed in combination with real-time noise standard deviation, and compensation is added to a known frequency band; for multi-bandwidth detection, wavelet packet decomposition is adapted to 100kHz-5MHz, candidate signals are marked when energy detection exceeds a threshold, and a range is determined by morphological filtering; extracting parameters such as center frequency, analyzing time-frequency characteristics through short-time Fourier transform, and calculating 4-order cumulants to establish feature vectors; coherent accumulation times are adjusted according to a signal-to-noise ratio, energy is superposed through phase alignment, and a purified signal is output through band-pass filtering. According to the invention, the signal detection precision and adaptability in a complex environment are improved, and misjudgment is reduced.

The invention discloses a high-precision magnetic field data acquisition unit for aeromagnetic measurement and an acquisition method thereof, belongs to the technical field of aeromagnetic measurement, and solves the problems that the acquisition resolution of an aeromagnetic measurement magnetic field is low, the measurement precision is influenced by a power supply and electromagnetic interference, and the data processing and storage reliability is insufficient. According to the invention, a framework of'acquisition module + control module 'is adopted, the acquisition module realizes high-precision sampling through low-noise power supply, differential reference and analog front-end full-link conditioning, the control module completes error compensation and aeromagnetic compensation through a Zynq core, and the 1nT-level magnetic field acquisition precision is achieved by matching an anti-interference design and stable storage and transmission. The 1nT-level magnetic field acquisition precision in the aeromagnetic measurement process is achieved, the signal acquisition precision and stability are remarkably improved, electromagnetic and power interference is effectively inhibited, the reliability of data processing, storage and transmission is guaranteed, and the strict requirements of aeromagnetic measurement for precision and interference resistance are met.

The invention discloses a subarray beam domain high-resolution spatial spectrum estimation method under an under-snapshot condition. The method comprises the following steps: step 1, uniformly dividing N-element towed linear array sonar array element frequency domain data into K subarrays; 2, performing beam forming processing on each piece of sub-array data to obtain a beam domain result of each sub-array; 3, calculating a beam domain steering vector; 4, calculating a beam domain covariance matrix; 5, realizing signal and noise power parameter estimation based on a sparse approximate minimum variance criterion; and 6, carrying out frequency band weighted summation on the estimated signal power to obtain a broadband DOA estimation result. According to the method, sub-array division dimensionality reduction, beam domain coherent processing and sparse parameter iteration estimation are combined for processing, the method has the advantages of low snapshot adaptability and high anti-interference capability, the method can be used for near-field weak signal detection of the towed linear array under multi-target interference, and effectiveness is verified through marine test data.

The embodiment of the invention provides a short-wave full-frequency staring-distributed cooperative frequency, channel and link measurement method. The method is applied to the field of short-wave measurement, and comprises the following steps: performing multi-phase filtering on a received broadband signal to obtain a multi-channel signal; determining signal power and noise power of the multi-channel signal, and determining frequency availability according to the signal power and the noise power; selecting an available frequency according to the frequency availability, measuring through a linear frequency modulation signal transmitted in a channel to obtain a channel characteristic parameter, and determining the channel availability according to the channel characteristic parameter; signals with different waveforms are transmitted in a specified link, link characteristics are obtained through measurement, and link availability is determined according to the link characteristics; the frequency availability, the channel availability and the link availability are subjected to statistical analysis to obtain a statistical analysis result, data support is provided for multi-link cooperative transmission strategy adjustment and link access decision, and the efficiency and reliability of short-wave communication are improved.

The invention relates to an LDPC (Low Density Parity Check) quantitative hierarchical decoding working method combining an improved dragonfly algorithm with residual degradation, and belongs to the technical field of wireless communication. The method specifically comprises the steps that firstly, a pilot signal is sent by a signal source, average least square estimation of channel state information is obtained through analysis based on representation of a received signal in a time domain and a frequency domain, noise power is determined, then the pilot signal is introduced into an improved dragonfly algorithm, quantization parameter set training is carried out, and the improved dragonfly algorithm reads a sample signal to obtain the channel state information. And finally, applying the self-adaptive quantization parameter set obtained by training to a residual degradation decoding algorithm, and if a decoding result does not meet a verification equation, carrying out next iteration. The performance of the residual degradation decoding algorithm is superior to that of the DLNMS, hardware resources are saved, the decoding performance of layered quantization is improved, the decoding time is shortened, and therefore the decoding speed is increased.

The invention provides a water quality suspended matter detection system and method based on sensing data, and belongs to the technical field of water quality suspended matter detection. Gain compensation is performed on a mixed optical signal based on backward spontaneous radiation noise power, so that the influence of self gain drift of a sensor and environmental interference on a signal baseline is effectively eliminated; the adaptive variational mode decomposition algorithm decomposes the standardized signal into a plurality of intrinsic mode functions, accurately extracts signals strongly related to the physical characteristics of the target suspended particulate matter, generates a particulate matter characteristic waveform signal with an optimized signal-to-noise ratio through the intrinsic mode functions screened out through weighted stacking, further highlights the time-frequency characteristics of the target signal, and improves the accuracy of the particulate matter characteristic waveform signal. Each independent particulate matter signal event is accurately separated by adopting a dynamic threshold peak value detection algorithm, and the detection accuracy is improved by extracting a multi-dimensional feature vector from each signal event and distinguishing target particulate matters from interferents by utilizing a pre-trained event classifier.

The invention provides an 802.11 be multi-user system receiver signal-to-noise ratio estimation method, device and equipment and a medium, and the method does not only depend on a limited number of pilot frequency subcarriers in a frequency resource unit where a target user is located any more, but analyzes and verifies an EHT-SIG field to estimate the signal-to-noise ratio of the target user. And a plurality of frequency resource units whose cyclic redundancy check results are verified to be correct are screened out, and all pilot frequency subcarriers contained in the reliable frequency resource units are combined to be jointly used for estimation. According to the method, a plurality of cyclic redundancy check results are combined to check all reliable pilot frequency subcarriers in a correct frequency resource unit to estimate the signal-to-noise ratio, so that the sample cardinal number of noise power estimation is remarkably increased; the problem of low estimation precision caused by too few pilot frequency subcarriers of a single user due to dynamic allocation in an 802.11 be multi-user system is effectively solved, so that the overall accuracy of signal-to-noise ratio estimation is improved.

The present disclosure provides a constant false alarm rate-based downhole casing nondestructive testing method, device and medium. The method can include: obtaining a detection threshold according to a preset false alarm probability and background noise power of a target pulsed eddy current array detection signal, wherein the false alarm probability refers to the probability that the detection system incorrectly determines the presence of a damaged target when a non-damaged target is present in the downhole casing; screening the target pulsed eddy current array detection signal based on the detection threshold to obtain a downhole casing damage detection result signal; and determining the position of the downhole casing damage according to the downhole casing damage detection result signal. Through this technical solution, the detection threshold can be dynamically adjusted, and the position of the downhole casing damage can be accurately located, thereby improving the efficiency and accuracy of downhole casing damage detection.

The application relates to a real-valued super-resolution direction estimation method of a high-order acoustic field sensor array, which uses a received signal covariance matrix to approximately calculate an estimated value of noise power, avoids the iterative operation process of noise power in the prior art, improves the calculation efficiency, and reduces the floating-point operation amount. By constructing an augmented matrix, the array receiving data matrix and the array manifold matrix with a multi-dimensional structure of an element are made into Hermitian matrices, so that the unitary transformation processing of the related parameters of the high-order acoustic field sensor array is realized. On the basis of obtaining the array receiving data matrix and the array manifold matrix in the real number domain, the array receiving data matrix and the array manifold matrix are applied to a sparse approximate minimum variance method with a variable exponential factor, and the completely real-valued sparse approximate minimum variance direction estimation with a variable exponential factor is realized.

The present application relates to the technical field of array signal processing and wireless communication, and particularly relates to a beacon source assisted self-calibration and robust beamforming method, comprising: collecting array snapshot data and constructing sample covariance; extracting spatial features based on coarse direction prior of auxiliary signal source and performing reliability determination; estimating geometric drift parameters through per-element phase ratio estimation; constructing parameterized covariance model based on calibrated array manifold and estimating noise power; estimating power coefficients of each signal source by using non-negative constraint fitting estimation; reconstructing INCM and optionally diagonally loading to enhance reversibility; calculating MVDR weight vector based on reconstructed INCM and outputting beamforming result; when reliability determination fails, falling back to nominal geometry or preset geometry to avoid false calibration. The present application has the advantages of geometric self-calibration, low snapshot robustness, false calibration prevention and wide application range.

The invention discloses a millimeter wave detection anti-noise performance improvement method and a millimeter wave detection anti-noise performance improvement system, relates to the technical field of anti-noise performance improvement, and is used for solving the problem of defect discrimination sensitivity and positioning precision reduction caused by insufficient identification accuracy of sound wave or radar detection in a high-humidity and high-noise tunnel environment. Target echo power is calculated by transmitting millimeter wave signals and receiving tunnel wall surface echoes, noise is collected and noise power is extracted, a gain adjustment coefficient is obtained based on the ratio of the two echoes, target signals are amplified, and a judgment threshold value is generated by combining wall surface material reflection characteristics so as to identify structural defects and generate abnormal information. The method comprises the following steps: adjusting the bandwidth of a receiving filter to obtain an optimized echo signal, analyzing the type, position and severity of a defect, extracting a multi-path echo delay difference to realize accurate positioning, and finally judging whether to generate early warning information or not by combining the delay difference and abnormal information, thereby improving the detection precision and response speed of the system under noise interference.

A method for monitoring generalized optical signal-to-noise ratio (gOSNR) is provided, which is applied to monitoring of an optical signal received by a coherent receiver through a fiber link. The method includes: obtaining a first received waveform; obtaining a signal part of the first received waveform; obtaining a noise part of the first received waveform according to the signal part and the first received waveform; obtaining a first correlation between the noise part and a first template at a predetermined location on the fiber link, the first correlation indicating a signal power at the predetermined location; obtaining a second correlation between the noise part and a second template at the predetermined location on the fiber link, the second correlation indicating a signal power and noise power at the predetermined location; and obtaining gOSNR at the predetermined location according to the first correlation and the second correlation.

The application discloses a speech enhancement method, device and electronic equipment, the method comprises the following steps: acquiring speech recognition confidence and a to-be-enhanced speech signal, and converting the to-be-enhanced speech signal into a frequency domain signal, wherein the speech recognition confidence is a confidence degree representing that the speech signal contains a user speech instruction; calculating a noise power estimation value based on the speech recognition confidence and the frequency domain signal; and performing adaptive beamforming by using the frequency domain signal and the noise power estimation value to obtain an enhanced speech signal. According to the technical scheme provided by the application, the speech recognition confidence of the speech signal is introduced to adjust the noise power estimation value, so that a more accurate noise power estimation value is obtained, and then the adaptive beamforming algorithm is executed based on the noise power estimation value, so that the speech enhancement effect can be improved in a low signal-to-noise ratio scene, and a more reliable enhanced speech signal is obtained.

The application belongs to the field of GPS positioning, and relates to a dynamic GPS signal interference influence evaluation method and system, which comprises the following steps: calculating the instantaneous position vectors and velocity vectors of visible satellites, a receiver and an interference source in the Earth-Centered Earth-Fixed coordinate system; obtaining the directional gain of a receiving antenna to multiple visible satellite signals and multiple interference signals respectively; calculating the noise power spectral density, the power of multiple visible satellite signals and the power of multiple interference signals arriving at the radio frequency front end of the receiver; modeling the equivalent carrier-to-noise ratio to obtain the equivalent carrier-to-noise ratio of multiple visible satellites; simulating the influence of the visible satellites on the code tracking loop of the receiver to obtain the pseudorange measurement error of multiple visible satellites; and performing positioning solution through a weighted matrix least square method to obtain the positioning accuracy, so that the interference effect can be accurately, real-timely and quantitatively evaluated.

The invention provides a medium-voltage line topology identification method based on a KNN classifier and a related device, and the method comprises the steps: collecting the signal power and noise power of topology identification equipment under different frequencies, and calculating the useful signal power of a self-transmitting and self-receiving micro-current and a self-transmitting and self-receiving micro-current; thirdly, in combination with an actual field shunting condition, taking frequency information, two types of useful signal power and shunting data as input, and training a KNN model; and finally, inputting frequency information of actual operation and two types of useful signal power into the model, adaptively outputting shunt judgment, and fusing non-shunt data to obtain actual topological information. According to the invention, through data training learning, the line shunting phenomenon is effectively identified, and the topology identification accuracy is improved.

The application relates to a channel estimation method, device, electronic equipment, storage medium and program product, and relates to the technical field of communication. The channel estimation method comprises the following steps: determining a pilot signal matrix according to the number of transmitting antennas and the pilot length corresponding to the communication signal of a target channel; constructing a to-be-processed matrix of the target channel according to the pilot signal matrix, the noise power of the communication signal and the number of receiving antennas; determining time domain weight and frequency domain weight based on a correlation influence parameter and a weight decision model; generating an iteration initial value according to the time domain weight, a first reference matrix corresponding to a second time slot and a first subcarrier, the frequency domain weight and a second reference matrix corresponding to a first time slot and a second subcarrier; performing iteration operation on the to-be-processed matrix according to the iteration initial value and a preset inverse iteration model; and obtaining the inverse matrix of the to-be-processed matrix to determine the channel matrix of the target channel when the preset iteration termination condition is met. The method can improve the communication performance.

The invention relates to the technical field of holography, in particular to a color hologram generation method based on an approximate secondary phase mask. The method comprises the following steps: constructing an approximate secondary phase; extracting an optimized approximate secondary phase mask from a spatial domain or a frequency domain according to the approximate secondary phase; and decomposing a target image into RGB three-channel amplitudes, and combining the optimized approximate secondary phase mask with the three-channel amplitudes to obtain a color hologram. According to the method, the calculation efficiency can be improved, a hybrid optimization strategy is provided, a high-quality initial phase is quickly generated through an approximate secondary phase mask, the phase distribution is refined by combining limited GS iteration (10-30 times), the single frame generation time is compressed to be within 5 seconds, the efficiency is improved by more than 50% compared with that of a traditional GS algorithm, high-frequency noise is inhibited through regular phase distribution, and the calculation efficiency is improved. The phase uniformity is improved in combination with double-domain optimization, so that the PSNR value of the reconstructed image exceeds 28dB, the SSIM value exceeds 0.9, and the noise power is reduced by more than 30% compared with a random phase method.

The invention discloses an interference suppression method, system and device based on frequency point quality cognition and a medium, and relates to the field of frequency hopping communication. A transmitting end adopts a frame structure of'synchronous head sequence + information sequence + synchronous tail sequence ', and forms a frequency hopping pulse signal for radiation after processes of coding, framing and frequency hopping modulation; a receiving end processes a received frequency hopping pulse signal after signal detection and timing synchronization, calculates a noise power value of each frequency hopping pulse after frequency hopping pulse synchronization head and tail sequences are correlated with a local sequence, calculates a noise weight value of each pulse, multiplies a weight factor with a pulse signal after channel equalization, and obtains a frequency hopping pulse signal. By reducing the signal observed quantity weight of the interfered frequency point, the influence of the confidence coefficient reduction caused by the interference signal on the channel decoding of the whole communication system is suppressed, so that the reliable transmission under the condition of low signal-to-noise ratio and strong interference is realized.

Various aspects of the present disclosure relate to methods and apparatuses supporting a dynamic signal to interference plus noise ratio (SINR) report in a lower layer split (LLS) radio access network (RAN) architecture. According to an embodiment of the present disclosure, a base station (BS) includes at least one memory and at least one processor coupled to the at least one memory and configured to cause the BS to: receive a set of signals on a set of physical resource blocks (PRB) sof a set of symbols from at least one user equipment (UE); and transmit a signal to interference plus noise ratio (SINR) report of the set of symbols to another BS, wherein the SINR report includes one or multiple SINR values of one or multiple PRBs of one or multiple symbols within the set of symbols, and wherein each of the one or multiple SINR values is defined as power of a signal received on the one or multiple PRBs divided by a sum of interference power and power of a background noise.

Provided is an interference removal device (1) capable of inhibiting deterioration due to noise emphasis. The interference removal device comprises: a data symbol extraction unit (11) for outputting a data symbol signal (101); a null symbol extraction unit (12) for outputting a null symbol signal (102); a data symbol power calculation unit (14) for calculating a data symbol power calculation estimation value (104); a null symbol spectrum calculation unit (15) for calculating a null symbol spectrum (105); an interference center frequency estimation unit (16) for outputting an interference center frequency estimation value (106); an interference bandwidth estimation unit (17) for outputting an estimation interference bandwidth (107); and an interference removal unit (18) for generating an interference replica signal and multiplying the interference replica signal by a weight factor for each frequency in accordance with the ratio of a noise power component and an interference power component included in the interference replica signal to thereby inhibit deterioration due to noise emphasis.

The invention provides a power line carrier communication method and device based on adaptive bit power allocation, and the method comprises the steps: determining the channel frequency response and noise power of each OFDM subcarrier according to a preset signal transmitted to a target electric energy meter and a receiving signal received by the target electric energy meter on each OFDM subcarrier, and transmitting the channel frequency response and noise power to the target electric energy meter; according to the method, the optimal activation subcarrier number with a good communication effect and the most appropriate optimal power allocation reference value are screened out through channel frequency response and noise power, and then target power and bit number are configured for each optimal activation subcarrier. According to the method, the OFDM subcarriers with better communication performance can be selected from the plurality of OFDM subcarriers, and then proper power and bit number are configured for each OFDM subcarrier, so that the data to be transmitted can be modulated to each optimal activation subcarrier to communicate with the target electric energy meter according to the target power and bit number. Therefore, the communication quality of the intelligent acquisition terminal is improved, and the probability of communication interruption is reduced.

The invention relates to the field of cell antenna factor calibration, in particular to a power domain estimation method and device based on GTEM cell antenna factor calibration. The scheme comprises the following steps: determining a working frequency band according to application requirements, and selecting a plurality of calibration frequency points in the working frequency band; performing reference field intensity calibration on each selected calibration frequency point; measuring an initial azimuth angle based on the GTEM cell; measuring noise power, and establishing a noise power matrix; measuring the receiving power under the full angle; subtracting the corresponding noise power from the measured receiving power to obtain net signal power; calculating an antenna factor of the antenna under the current set angle and the calibration frequency point according to the antenna factor definition; and finally, calibrating and verifying the antenna factors. The method is suitable for power domain estimation based on GTEM cell antenna factor calibration.

This invention relates to an FPGA-based method, apparatus, and system for calculating the approximate log-likelihood ratio (ALLR). The method includes: receiving a communication data frame via a receiver; performing a conjugate multiplication of the training sequence symbols in the communication data frame with local training sequence symbols to obtain the conjugate multiplication result; using a first FPGA circuit to obtain the signal amplitude and noise power based on the conjugate multiplication result; obtaining a calculation formula for the approximate log-likelihood ratio based on the signal amplitude and noise power using the max-log-map algorithm; and using a second FPGA circuit to obtain the approximate log-likelihood ratio result of the communication data frame based on the signal amplitude, noise power, and the calculation formula, thereby decoding the data sequence in the communication data frame according to the approximate log-likelihood ratio result. This approach fully considers the impact of signal amplitude and noise power on the ALLR, helping to improve the accuracy of the ALLR calculation and enabling the decoder to achieve optimal decoding performance.

The application provides a kind of high-frequency oscillation detection method based on band adaptive anti-noise power system, comprising: installing three-phase high-frequency voltage transformer at resonance sensitive point, selecting data acquisition window width, collecting three-phase voltage data and constructing three-phase voltage tensor mathematical model;Voltage tensor in three-phase voltage tensor mathematical model is decomposed to Tucker to realize voltage denoising;The voltage tensor after denoising is converted into three-phase voltage, and peak detection is carried out using dynamic measure;According to the detected high-frequency oscillation signal and its frequency range, wavelet packet decomposition is carried out on three-phase voltage, so that high-frequency oscillation signal and low-frequency fundamental wave and related harmonic components are separated to the wavelet coefficients of each frequency band;The wavelet coefficients containing oscillation signal are subjected to oscillation signal restoration;The restored oscillation signal is subjected to exponential decomposition using Prony method, and high-frequency oscillation characteristics are obtained.The application can improve the detection accuracy of high-frequency oscillation.

Disclosed herein is an apparatus of a communication device, the apparatus includes a processor configured to estimate noise power characteristics within a frequency band based on a received signal comprising a plurality of subcarriers within the frequency band, wherein the noise power characteristics comprises a plurality of noise samples. The processor is also configured to estimate a noise covariance matrix by averaging a number of noise samples of the plurality of noise samples. The processor is also configured to apply a whitening that is based on the noise covariance matrix to subsequent received signals.

A method for measuring a sensitivity of a receiver is provided. The method includes: during a first stage, controlling a signal generator to transmit an input test signal to an input node of the receiver, wherein the receiver generates an output test signal on a first output node of the receiver according to the input test signal; calculating a path loss from the input node of the receiver to the first output node of the receiver according to the input test signal and the output test signal; during a second stage, measuring an output noise power on a second output node of the receiver after a load is connected to the input node of the receiver; and calculating the sensitivity of the receiver according to the path loss and the output noise power. The load may be an antenna or a 50-ohm impedance load.

The invention discloses a self-adaptive carrier frequency point and bandwidth filtering noise reducer and a method thereof. The method comprises the following steps of: dividing the whole receiving bandwidth of a receiver into N segmented frequency spectrums; calculating N noise power thresholds corresponding to the N segmented spectrums, and setting cascaded N noise elimination modules according to the N segmented spectrums and the N noise power thresholds; the method comprises the following steps: inputting carrier data into cascaded N noise elimination modules, filtering an ith segment frequency spectrum through an ith noise elimination module to obtain ith segment frequency spectrum filtering data, calculating the average power of the ith segment frequency spectrum filtering data, comparing the average power with an ith preset noise power threshold value, if noise is judged, subtracting the noise from the original carrier data, and if the noise is not judged, subtracting the original carrier data from the ith preset noise power threshold value; and if the ith section of spectrum data contains signal data, reserving the signal data, and directly outputting the input signal of the ith noise elimination module as the input signal of the (i + 1) th noise elimination module. According to the method, the noise can be effectively reduced in a self-adaptive manner under the condition that the carrier frequency point and the bandwidth are unknown.

This application discloses a method and product for self-diagnosing external interference. The method includes: acquiring the inherent parameters of the frequency-using terminal to calculate the theoretical noise floor; measuring the total received power in real time and calculating the super-noise power accordingly; when the super-noise power exceeds a preset power threshold, acquiring the baseband demodulation quality parameters of the current channel; and performing correlation discrimination based on the super-noise power and baseband demodulation quality parameters. When the super-noise power is high and the demodulation quality is below a preset threshold, it is determined to be external interference; otherwise, it is determined to be a strong useful signal. This application establishes a two-dimensional causal correlation model between physical layer power and baseband layer quality within the terminal, enabling real-time and objective self-diagnosis of external interference from the terminal's own perspective, thus improving the objectivity, timeliness, and accuracy of the diagnosis.

The invention discloses an efficient soft demodulation method and system suitable for pulse position modulation, and relates to the technical field of laser communication. Pulse position modulation signals and preset channel parameters are received, and time slot receiving signals are acquired based on the pulse position modulation signals, the preset channel parameters comprise the optical signal intensity and noise power of a Gaussian channel, the pulse optical signal electron number of a Poisson channel and the electron number of an ambient optical signal; inputting the time slot receiving signal and a preset channel parameter into a pre-established soft demodulation model based on a maximum posteriori and a maximum likelihood criterion, and outputting to obtain a log likelihood ratio LLR of a modulation bit; meanwhile, the index logarithm operation of the LLR is simplified by adopting a max-log method, and the calculation complexity is reduced; aI is adopted to optimize the scaling coefficient for the performance loss caused by soft demodulation calculation simplification to balance the performance loss and the implementation complexity, so that the transmission efficiency of PPM modulation is improved.